What I want to do is to make the textbox always fill-in the available space between the label and the right border of the container, even when window is resized

The label is set to be AutoSize because it has different width in different languages.

I tried the flow layout, and I also tried various combinations of dock/anchor in both elements, but still can't make it work. If there is not simple solution (beside program coding resizing myself), is there a less optimal solution? Thanks.

I just tried this but textbox will fill underneath the label too
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lulalalaJun 30 '11 at 13:43

You have to make sure the z order of your controls is correct. Z order is generally set based on which control is added to the design surface first. Click on one of the controls and select either Bring to Front or Send to Back and it should take care of it for you. It's been a while since I've worked with winforms so I'm not 100% sure where those commands are located, but I'm fairly sure they are on the context menu somewhere.
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John LaffoonJun 30 '11 at 14:02